Electrode for spark plugs



April 15, 1924. I 1,490,364

E. T. CURRAN ELECTRODE F R SPARK PLUGS Filed June 6. 1921 Fig, i

[N VEN TOR. fo wa/"o I Curran BY ATT 1v Y5.

Patented Apr. 15, 1924.

i star ELECTRODE FOR SPARK PLUGS.

-application filed June 6, 1921.

To all whom'c't may concern. 7

Be it known that i, EDWARD T. CURRAN, a citizen of the United States, residing at Detroit, in the county of Wayne, State of Michigan, have invented certain new and useful Improved Electrodes for Spark Plugs, of which the following is a specification. I

This invention relates to spark plugs and is particularl directed to the manner of forming the electrodes of the plug to provide a highly eliicien't gap in which the sparking which ef ects ignition occurs.

In the plug of the present invention, the gap is formed between upstanding edges which are preferably sharpened to a knife edge and are, in the preferred form of the invention, in slightly upward converging relation, so as to provide a spark gap of varying width.

It has been heretofore suggested to provide a plug with one knife edge electrode and this electrode has been supported by a grounded shell. The central electrodes of theprior plugs have in every instance been inv the form of straight rod and the knife edge has been formed parallel to the rod.

The function attributed to this construcion in prior plugs is the production of a fan-like flame to produce the desiredignition.

I have found in practice that in a cylin der containing more or less lubricating oil, due to leaky valves or piston rings, that the oil in the cylinder works up into the plug chamber and dribbles down the central electrode forming a globule at the bottom thereof, which greatly decreases the normal spark gap with the result that the plug becomes at least partially shortcircuited, accumulates carbon rapidly and ceases to function with maximum efficiency.

\Vith the foregoing considerations in mind, the object of the present invention is to provide a plug which will not be short circuited in the manner described and this object is obtained by the formation on the central electrode of aradially extending arm the outer end of which carries an upstanding knife edge, so that any oil which may flow down the central electrode will not How over the laterally positioned knife edge and consequently will not decrease the size of the gap.

in making the plug of the present invention, the opposed knife edges between which Serial No. 475,209.

the gap is formed may diverge longitudinally so as to form a tapering gap for the purpose of compensating for different engine'speeds, although, in practice, said knife edges may be parallel to one another so as to provide a gap of the same dimensions throughout.

Features of the invention, other than those specified, will be apparent from the hereinafter detailed description and claim, when read in conjunction with the accompanying drawings.

The accompanying drawings illustrate different practical embodiments of the invention, but the constructions therein shown are to be understood as illustrative, only, and not as defining the limits of the invention.

Figure 1 is a side elevation of a spark plug with the lower portion thereof shown in central section and illustrating the present invention associated therewith.

Figure 2 is an underneath plan view of the lower portion of the plug of Figure 1.

Figure 3 is an enlarged diagrammatic showing of the two electrodes of the plug; and,

Figured is a section of a lower end of modified form of plug.

Electrodes constructed in accordance with the present invention may be associatedwith any conventional type of plug, but for the purpose of illustration, 1 have shown the same as embodying a construction of a plug forming the subject matter of my copend ing application case F, filed on even date herewith.

Practically all plugs of the conventional types embody a central electrode 1, which is included in circuit with the magneto, storage'battery orother source of current supply by an ignition lead secured to the upper end of the plug. The other electrode of the plug is designated generally by the reference character 2 and is supported on the shell or nipple 3 of the plug adapted to be screwed into the spark plug hole of a. cylinder, so as to ground the electrode 2.

In accordance with the present invention, the electrode 2 is mounted on the interior of the nipple 3 and adjacent the lower end thereof and projects inwardly of the nipple in a a substantially radial direction. The inner end of the electrode 2 extends up wardly in the form of a prong and the free or substantially vertical edge of the prong is sharpened to a knife edge. The central electrode 1 has formed on the lower end thereof a prong 5 of the same general shape and construction as the prong 2 and the upstanding edge 6 of said prong 5 is also sharpened to a keen knife edge.

In practice, the knife edges 4 and 6 may be made parallel as shown in Figure 4, but it is preferred to construct them in such manner that they will slightly converge in an upward direction. By thus forming the knife edges L and 6, the spark gap between said edges par-takes of a tapering form. During normal operation of the engine at low speeds, the current will jump the gap at its smallest dimensions namely adjacent the upper ends of. the prongs. However, as the engine speeds up, and in the case of magneto ignition more current is supplied to the plug, the current will jump the gap in greater volume and the flame will creep down the gap and broaden or flare out in a vertical plane, so that a more intense and hotter spa-rk will result. l/Vhen the engine is operated at its highest speeds, the entire gap of the plug may be filled with flame. In this manner, the plug may be constructed to compensate for varying engine speeds in an entirely automatic manner. I

In the construction of Figure 4, the spark will jump the same gap at all speeds, but will increase in intensity and volume as the engine speed increases.

It is entirely practical to make the upstanding edges 4 and 6 of the electrodes dull instead of sharp or knife edge as described, and the present invention is not restricted to a knife edge. ,However, such knife edges are preferred for several reasons. In any event, it is desirable to at least taper the electrodes toward the edges 4 and 6. The reasons for tapering the electrodes in the manner described will clearly appear from Figure 3 of the drawings, wherein a number of arrows are shown indicating the course of heat absorbed by the electrodes. Thorough experimentation has convinced me that when a relatively sharp or line-like edge is formed with a backing of materially greater dimensions that heatabsorbed by the heavy backing will rapidly rush to the knife edge and be radiated therefrom. Thus, if the prong 5 of the electrode 1 is sharpened along the edge 6, I have found that the heat which the electrode 1 takes up adjacent the prong will rapidly find its way to the sharp edge 6 and this is also true of the heat taken up by the prong 2 which will with equal rapidity find its way through the knife-like edge a. The knife edges accordingly will be heated to a high temperature, so high a temperature, in fact, as to preclude the lodging of globules of lubrication oil thereon, even though such edges were so positioned that they would be in the natural flow of the oil.

Accordingly, any oil which splashed upon such knife edges will be immediately borne of? and said edges will remain clean through long periods of use even when employed in cylinders which are flooding with oil.

In the practical carrying out of the invention, the knife edges preferably converge in an upward direction and the prongs are preferably positioned in substantially upstanding relation to one another. However, if desired, the prongs may be made so as to converge downwardly or extend in any other direction without departing from the spirit of this invention, the scope of which is commensurate with the appended claim.

Having thus fully described the invention. what I claim as new and desire to secure by Letters Patent is:

A. spark plug embodying a shell, a central electrode coaxial of the shell, a spur integral with the central electrode and an tending radially therefrom in an outward and upward direction from the lower end of the central electrode and terminating in an upstanding knife edge, and a spur extending radially inwardly from the shell toward the spur of the central electrode and in an upward direction and terminating in an upstanding knife edge spaced from the knife edge of the spur of the central electrode and forming between these knife edges a spark gap, whereby oil flowing down the central electrode or the interior of the shell will not impinge said knife edges, said electrodes being positioned interiorly of the plug.

In testimony whereof I have signed the foregoing specification.

EDWARD 'r. (manner.

may be 

